The invention relates to a method for encapsulation of an edible oil, to compositions comprising edible oil; to food products comprising these compositions; and to the use of these compositions.
Edible oils that contain unsaturated fatty acids, and especially polyunsaturated fatty acids (PUFAs), usually in the form of glyceride esters, have been shown to have beneficial health effects. These health effects include the reduction of cholesterol levels, protection against coronary heart disease and suppression of platelet aggregation. For example, fish oils and fungal oils, which contain for instance the omega-3 and omega-6 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), have been used in food products and in nutritional products for its health benefits.
One problem with PUFAs is that these have a tendency to undergo oxidation, which may result in these oils being less active, and which may result in an unpleasant taste and/or odour. This tendency to oxidize increases when the PUFAs are stored for a prolonged time; that is, the shelf or storage stability is relatively short because of the problems associated with the tendency to undergo oxidation.
To protect PUFAs, these have been incorporated into a protective matrix. WO-A-01/74175, for instance, discloses a method to obtain a powder containing an encapsulated oxygen sensitive oil. In this method, a protein solution, and preferably a casein containing solution, is heated in the presence of a carbohydrate in such a manner that a Maillard reaction occurs. Subsequently, oil is added to the mixture, followed by emulsification and drying. The essential Maillard reaction provides resistance to oxidation to the particles.
In EP-A-1 616 486, powdered compositions are described which comprise edible oil, sugar alcohols and reducing sugars. The combination of glucose syrup with mannitol provides the powders with an improved stability in a dry form to oxidation, and better taste and/or odour. However, the achieved stability is not maintained in liquid applications due to the fast solubilization of these powders, releasing the poorly protected oil emulsion droplets that were entrapped in the sugar matrix; that is, these encapsulates only show limited functionality in liquid applications.
WO-A-2008/143507, WO-A-2009/070010 and WO-A-2009/070011 concern methods for manufacturing microcapsules containing a hydrophobic core and a protein-based shell encompassing activation of protein particles, which step is said to be “a special form of protein denaturation” and which step is “crucial for the formation of disulphide cross-links during subsequent encapsulation steps”. The activated proteins form a layer at the interface of a hydrophobic dispersed phase and a continuous aqueous phase, and are subsequently cross-linked by forming disulphide cross-links. After this cross-link formation, the product may be spray-dried. Such encapsulates, however, do not provide a good shelf stability in dry form, as is shown herein-below in Examples 4-6 where Example 6 is a system in conformity with WO-A-2009/070010. In addition, these encapsulates cannot be obtained within small particle size ranges (e.g. from 0.5 to 10 μm) by using industrially practical production techniques such as spray drying.
WO-A-2005/048998 teaches a method wherein a core material is selected; a film forming water soluble protein and carbohydrates are dispersed in an aqueous phase and either not heated or heated to such an extent that Maillard reaction products are formed; the core material and the protein-carbohydrate dispersion are mixed and homogenized to obtain an emulsion wherein the core is surrounded by an encapsulating protein-carbohydrate mixture; and optionally spray drying.
US-A-2008/095907 describes an encapsulant for oxygen sensitive oils prepared by reacting an aqueous mixture of a protein (casein, whey protein) with a carbohydrate containing reducing sugar such as glucose and lactose, so that a Maillard reaction occurs. It is state of this document that the Maillard products protect the encapsulated oil from oxidation.
Particularly, in the method of US-A-2008/095907 proteins are first dispersed in water, after which carbohydrates containing reducing groups are added. The solution obtained in heated at 90-100° C. for 30-90 minutes and cooled down to 50° C. Subsequently, an oil heated to 50-60° C. is added to the protein-carbohydrate solution and the resulting mixture is homogenized and spray-dried.
Encapsulated products often suffer from the problem of diffusion of the encapsulated ingredients or diffusion of off-flavour components generated by such ingredients out of the microcapsules into the surrounding phase, when these encapsulated ingredients are incorporated in liquids, such as milk, dairy products, juices, etc. While for powdered compositions mainly the dry storage stability of microcapsules is important, in liquid applications also a longer stability in solution/dispersion and a limited diffusion into the continuous phase are particularly desired. Also diffusion from the continuous phase into the microcapsules is a factor that can affect oxidation; such diffusion processes are dependent on microcapsule characteristics. As a result of diffusion, the encapsulated oils can be exposed to prooxidants present in the liquid, leading to a faster oxidation, which negatively affects the taste and/or odour of the liquid products.